In VyOS 1.2.0 RC3 the following error occures:
vyos@vyos-test01:~$ monitor traffic interface eth1 filter "host 172.16.10.104" tcpdump: syntax error
But not all filters are affected. The following works:
vyos@vyos-test01:~$ monitor traffic interface eth1 filter "icmp"
The same filter in tcpdump works:
sudo tcpdump -i eth1 "host 172.16.10.104"